sedimentary
Quartz pebble
Silicon dioxide (SiO2)
Hardness of 7 on the Mohs scale, typically brown, tan, or clear in weathered river pebbles, vitreous to greasy luster, trigonal crystal system when formed well but amorphous/rounded as a pebble, no cleavage, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically brown, tan, or clear in weathered river pebbles, vitreous to greasy luster, trigonal crystal system when formed well but amorphous/rounded as a pebble, no cleavage, specific gravity of 2.65.
Formation & geological history
Formed through the weathering and erosion of parent igneous or metamorphic rocks, subsequently transported and rounded by water action in rivers or streams over thousands to millions of years.
Uses & applications
Used in landscaping, decorative gravel, construction aggregate, and as tumbling rough for hobby lapidary work.
Geological facts
Quartz is one of the most abundant and durable minerals in Earth's continental crust, highly resistant to both chemical and mechanical weathering, which allows it to survive long journeys in riverbeds.
Field identification & locations
Commonly found in stream beds, beaches, and alluvial gravel deposits worldwide. Identified by its high hardness (scratches glass), lack of cleavage, and smooth water-worn shape.
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